The new bus design mimics some of the features of the iconic red London Routemaster bus – and seven of them are scheduled to come into service in February 2012.

The iconic buses were withdrawn from regular routes in 2005 in favour of newer single-decker "bendy buses".

The first of the new buses will be operated by transport company Arriva. It will enter passenger service on 20 February 2012 on route 38, which runs from Victoria station to Hackney in east London.

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Boris hailed the fact that the bus was designed and made in Britain, unlike the German bendy buses, and also highlighted the fact they will be the most environmentally friendly mode of public transport on London's roads.

He said he hoped hundreds of the hop-on hop-off designs would be on the city streets over the next few years.

The cost per bus for employing a second staff member to man the hop-on hop-off service will be around £62,000 a year.

Labour critics have attacked the project, claiming it is nothing more than a 'vanity project', suggesting that is excessive at a time when fare prices are rising sharply and Britain is facing another recession.

The cost for developing the new prototype Routemaster bus and a contract for eight production models has so far cost Transport for London £11.37 million.

Critics have also lambasted the fact that the new bus design has a far lower passenger capacity, and so might lead to overcrowding.